Insulated wires, which are used as wiring in railroad cars and automobiles, are required to have not only the insulation property but also such a flame-retardant property as making the wires difficult to burn at the time of fire. For this reason, a flame retardant is contained in a coating layer of the insulated wire. For example, Japanese Patent Application Laid-Open Publication No. 2014-11140 (Patent Document 1) discloses an insulated wire having a coating layer formed by stacking a flame-retardant layer containing a flame retardant on an outer periphery of an insulating layer having an insulation property. According to the Patent Document 1, the insulation property and the flame-retardant property can be well balanced at a high level.